The present invention generally relates to actuators, and in particular relates to a trigger actuator assembly for a firearm or similar hand-operated device for controlling the initiation of a firing sequence or operation of the firearm or other hand-operated device.
Actuator systems for most firearms and other hand-actuated, similar devices traditionally have been substantially mechanical systems, relying on levers, cam surfaces, and springs set into motion by the squeezing of a trigger to activate a switch or initiate the operation of the device. For example, with most conventional firearms, the squeezing of the trigger releases a firing pin to strike and thus set off a primer charge such as for a round of ammunition. Being primarily mechanically based, such systems generally require close manufacturing tolerances and further inherently suffer from limitations in control of the actuation or operation of the device or other problems such as discontinuities in the trigger pull force. In addition, in most conventional mechanically activated firearms, there is often a shifting and/or an audible knock or click as the sear is disengaged from the firing pin to enable the firing pin to be moved into contact with the primer. Further, over time, the use and motion of such mechanical assemblies tends to cause wear on the mechanical parts that can result in further discontinuities in the operation of the trigger or actuator assembly. The fact that most mechanical triggers require considerable trigger engagement, trigger movement from the starting point to the point of activation, as well as the inherent inconsistencies and discontinuities can significantly affect the operation of the device, such as diminishing or otherwise affecting the accuracy of a firearm by causing the shooter to anticipate the shot and shift or move the firearm during the trigger pull.
Electrical and electromechanical actuator assemblies or mechanisms using electromagnets, solenoids and/or piezo-electric elements have been proposed, including for use in firearm trigger assemblies, wherein an electromechanical switch or other electric element is engaged by the movement of the trigger to cause the release of the firing pin for engagement and setting off of the round of ammunition. Such systems, however, still generally have a significant, mechanical component, as they typically still include a series of mechanical linkages and elements that move and engage an electronic switch for activation of the device. Thus, these electrically actuated systems can still suffer from the discontinuities and other problems inherent in mechanical actuator assemblies.
Therefore, it can be seen that a need exists for an actuator assembly with a reduced number or substantially no moving parts, and which thus substantially eliminates the problems inherent in most mechanical actuator assemblies.
The present invention relates to a trigger actuator for initiating and controlling the operation of a hand-actuated/operated device, such as for controlling operation of a variable speed drill, saw or similar hand-activated tool, and in particular for initiating or setting off a primer charge for a round of ammunition in a firearm or a shot charge or power load for driving a fastener. The actuator generally includes a trigger assembly having a body and trigger that is formed with and projects from the body so that the trigger assembly has a substantially unitary or one-piece construction so as to require substantially no movement thereof for actuation, and a controller that typically comprises a microprocessor.
In an initial embodiment, a first or trigger measuring device, such as a strain gauge, load cell, transducer, force-sensor, force sensing resistor, conductive rubber, piezo-electric sensor, piezo-resistive film or similar type of sensing element is mounted adjacent the trigger to detect and measure a force applied to the trigger by the user. Typically, the first measuring device will be positioned along the trigger or along a cantilever or extension section formed between the trigger and body of the trigger assembly, or at a desired position along the body. The measuring device detects the application of force to the trigger and generates a trigger signal in response. A cavity, notch, bump, or other sensitivity increasing feature also can be formed in the body, trigger, or cantilever for increasing the sensitivity of the measuring device to detect a force applied to the trigger to ensure that the application of force to the trigger will be detected by the trigger-measuring device. The trigger signal from the trigger measuring device is received by a control system which in turn initiates the operation of the device to which the actuator assembly is mounted.
In a further embodiment, a compensating system is provided for compensating for variances or errors in the trigger signal provided by the trigger-measuring device. The compensating system can include both mechanical and electrical components. For example, in one embodiment of the present invention, a compensating mass can be formed with the body of the trigger assembly, supported by a compensating cantilever. In such an embodiment, a second or compensating measuring device, such as a strain gauge or similar sensing element will be mounted to the compensating cantilever or mass. If the device or system in which the actuator is used is inadvertently jarred or receives a shock or other force, such as from being dropped, as opposed to the application of force to the trigger alone (i.e., squeezing of the trigger), the compensating measuring device for the compensating system will record and generate a compensating signal similar to the trigger signal so as to cancel an undesired trigger signal. Further, the measuring devices can be configured opposite in polarity to provide the additional feature of self-compensating for variations in the measurement device itself, such as, for example, by canceling any errors induced through variations in operating temperature.
The compensating system also can include an amplifier that combines and potentially modifies the trigger and compensating signals, and/or a filter system employing low pass, high pass or band pass filters for monitoring the rate of change in the trigger signal. Thus, if the trigger signal rate of change is provided at a rate that is too fast or too slow, so as to fall outside of a predetermined operating range, as would be the case if the trigger were jarred or subjected to extreme temperatures, the trigger signal will be blocked or filtered from being transmitted to the actuator control system.
The control system of the actuator assembly generally includes a controller for processing inputs from the trigger assembly and compensating system, which generally is a microprocessor. The controller can be programmed with pre-determined operating ranges for the rate of change of the trigger signal and can include the filter and/or a comparator system. The controller receives the trigger signal and any input received from the compensating system and, in response, initiates an operational sequence. For example, the comparator system will receive and compare the trigger signal to a pre-determined or pre-programmed reference such as a programmed voltage reference. The voltage reference typically is variable and can be set as a predetermined value or range of values such that if the trigger signal falls outside of this range, the trigger signal is blocked, and the variability of the voltage reference further enables the adjustment or setting of a desired trigger pull that is consistently required for initiating an operational sequence.
The controller can be a separate processor that processes and controls the inputs from the trigger assembly and compensating system of the present invention, or can be the electronic controller for the device, such as an electronic firearm as disclosed in U.S. Pat. No. 5,755,056, for operation with both percussion actuated primers or ammunition and with electrically actuated ammunition primers. Further, the controller may directly incorporate the compensation system directly via digital signal processing (DSP). Those skilled in the art will understand that low pass, band pass, high pass, and notch filtering techniques can be performed either via external analog components (resistors, capacitors, op amps, etc.) or by DSP Z Transform processing techniques.